An antimicrobial polymer composition comprising a polymer and an antimicrobial composition having an antimicrobial coat of an aluminosilicate on the surface of silica gel, wherein said aluminosilicate containing antimicrobial metal ions, such as silver, copper and zinc, is disclosed in the U.S. Pat. Nos. 5,244,667 and 5,298,252.
Since said antimicrobial composition is effective against common fungi and also exhibits excellent biocidal activity against mildew, research and development leading to new applications have been carried out. Furthermore, research and development of an antimicrobial polymer composition comprising said antimicrobial composition is also carried out and some uses have been developed.
However, if said silica gel based antimicrobial composition is added to a polymer and molded under heating, it is known that an undesirable discoloration or coloring occurs in some polymers under certain processing conditions, due to an interaction of antimicrobial composition with polymer or an interaction of antimicrobial composition with additives or catalyst contained in a polymer.
Furthermore, an antimicrobial polymer molding may discolor or degrade with time and an economical value may be damaged. In some polymers, a discoloration is accelerated by a radiation of sunlight or ultraviolet light.
Many researches have been carried out to resolve the defects of the prior antimicrobial polymer composition containing the above mentioned antimicrobial composition. A discoloration resistance and a weatherability are improved, however, they are not satisfactory, yet. The technology that can prevent a coloration which occurs during blending or molding under heating or a variety of the molded article with time has not been developed.
Accordingly, it is desired to develop a novel technology that can prevent a discoloration or coloration of the antimicrobial polymer composition and improve the weatherability. The main object of the present invention is to provide a novel antimicrobial polymer composition which resolves the above mentioned defects of the prior art.